Hi,

I would like to propose this (possible) patch.

With `#+STARTUP: macro-arg-sep-other' the macros arguments can be
separated by a string other than comma, whose value is defined in
`org-macro-arg-sep-other' (by default it is "'@").

Rationale for this patch: There are many contexts where the comma character can be
inappropriate as an argument separator, since it has to be escaped many times.

If the patch is relevant, I can take care of writing the documentation and docstrings.

Example:

#+begin_src org
  ,#+STARTUP: macro-arg-sep-other
  ,#+MACRO: lg (eval (if (org-export-derived-backend-p org-export-current-backend 'latex) (concat "@@latex:\\foreignlanguage{@@" $1 "@@latex:}{@@" "\u200B" $2 "\u200B" "@@latex:}@@") $2))

  {{{lg(latin'@Lorem ipsum dolor sit amet, consectetuer adipiscing elit, donec hendrerit
  tempor tellus, donec pretium posuere tellus, proin quam nisl, tincidunt et, mattis eget,
  convallis nec, purus.)}}}

  With the escaped character:

 {{{lg(latin'@Lorem ipsum dolor sit amet \'@)}}}
#+end_src

Best regards,

Juan Manuel